This research project integrates our clinical and basic science interest, and is designed to identify objective biochemical measurements in sperm which are important in the prediction of fertiziling potential of male infertility patients. The proposed experiments are directed to sperm metabolism, and in part are designed based on the creatine phosphate shuttle hypothesis. This idea suggests a central role of creatine phosphate in energy transport, and the importance of creatine kinases in the mitochondria and flagellum of sperm in the synthesis and utilization of energy. We have found a correlation between the creatine kinase activity and the number of motile sperm in various specimens, and a statistically significant increase in creatine kinase and dynein ATPase (the principal structural protein and enzyme in sperm motility) activities of oligo/asthenospermic specimens. Furthermore, we demonstrated an enhancement of sperm velocity and motility index in response to creatine phosphate, and the presence of the mitochondrial type and brain type creatine kinase isozymes in human sperm. We also plan to perform chemical modifications of creatine kinase with fluorodinitrobenzene in live sperm, which will allow further quantification of creatine kinase in sperm, and may indicate the metabolic reserves available in various sperm specimens. With respect to structural proteins, we will quantify and determine the source of the unusual amino acid, 3-methylhistidine in sperm. Since this methylated amino acid has only been found so far in contractile proteins and excitable tissues, it may contribute to our understanding of the mechanism of sperm motility. The possible correlation between the biochemical measurements of creatine kinase and dynein ATPase activities, creatine kinase isozyme ratios, and between the conventional sperm analysis parameters (concentration, motility, velocity, and morphology) will aid in the evaluation and classification of the male infertility patients. We expect that this complex assessment of sperm function, combined with the fertility experience of the about 320 infertile couples in our intrauterine insemination program, will give us clear indication as to which of the parameters may be predictive to fertility/infertility. Thus, the proposed research project will introduce several new approaches in the diagnosis and treatment of male infertility patients.